Adjustable chair

ABSTRACT

An adjustable work chair such as an office chair has a height-adjustable seat comprising a front seat part ( 2 ) and a rear seat part ( 3 ) connected by a hinge ( 4 ) that extends transversely of the seat. A first arm ( 15 ) is coupled between the front part of the seat and the head of a fixed part ( 13 ) of a seat lift ( 14 ), and a second arm ( 16 ) is coupled between an extendable piston of the lift ( 14 ) and the underside of the rear part ( 13 ) of the seat.

FIELD OF THE INVENTION

This invention relates to a chair, for example an office chair, having aheight-adjustable seat.

BACKGROUND OF THE INVENTION

DE 43 03 021 A1 discloses an adjustable work chair of this type in whichthe seat comprises a front part and a back part connected by atransverse hinge and including a first arm connected to the front partof the seat near its front edge and a second arm connected to the backpart of the seat. The seat is height-adjustable by means of a lift andcan be progressively tilted forwardly from a normal position to an angleof about 15°. The tilt is such that the entire thigh part of a user'sleg rests on the seat when the lower part of the leg is extendsvertically. A standing work position cannot be achieved with this chair.

Ergonomists and occupational health workers have repeatedly commented onthe benefits to health of frequent changes from a seated position to astanding position. New work desks offer an adjustment range from seatedto standing work positions. Therefore, there is a need for work chairswith an adjustment range between seated and standing work positions.This does not merely involve enlargement of the adjustment range, whichwould lead to sitting at standing height, as with bar chairs or chairswith a foot ring for stand-up counters. Rather, the standing workposition should allow for leaning or short-term crouching to relieve thefeet.

EP 0 293 136 B1 and 0 371 729 B1 disclose chairs with seats that aresaddle-shaped and that swivel to allow leaning or short-term crouchingin the standing position of the seat. A disadvantage here is that asit/stand position or a seated position on a tilted seat are notpossible because of the saddle shape of the seat.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved adjustablework chair providing sit/stand positions.

In accordance with one aspect of the invention, there is provided achair having a height-adjustable seat comprising a front seat part and arear seat part connected by a hinge that extends transversely of theseat. The chair has a lift for raising and lowering the seat and thelift includes a fixed part and a movable part that can be extendedupwardly with respect to the fixed part. A first arm is connectedbetween the front part of the seat and the fixed part of the lift, and asecond arm is connected between the movable part of the lift and therear part of the seat.

A work chair of this form is adjustable in the sense of the invention inthat it is possible to lift the seat from the normal seated position insuch a manner that the front part of the seat is turned through an angleof at least 60° from the horizontal. Simultaneously, the back moves upparallel to its original position and a sit/stand or a stand/leanposition may be assumed.

A user of the chair may relieve his or her feet by crouching into therear part of the seat, to which a back rest may be fitted.

Preferably, the seat is divided so that the hinge lies towards the rearof the seat, with the front part forming between a half and two thirdsof the overall depth of the seat. A mechanical arrangement allows thefront part of the seat to tip downwardly in the upper position. As aresult, a shorter seat is presented in the standing or leaning position,as with a high stool. In the sit position, the seat returns to itsnormal, office chair position and an additional resting position can beattained by tipping the rear part of the seat backwards.

In a first embodiment of the invention, the first arm of the chair ismovable both at the front part of the seat and where it joins themovable part of the lift (e.g. the head of an extendable piston). In thesecond embodiment, the first arm is joined to the front part of the seatso that it is movable but is firmly attached to the fixed part of thelift (e.g. a cylinder receiving the piston). In these two embodiments,the lift may be a gas spring having two individually adjustable liftheights of 190 mm.

The first lift height regulates the seat height between about 400 mm and590 mm. The second setting regulates the lift from the sit position tothe sit/lean position through about 780 mm. Both lifts can be regulatedindividually so that the second setting is fully expanded in the standposition and the height can be adjusted individually for a small personby means of the first setting. Furthermore, the forward angle of theseat can be regulated individually with the second setting.

In a third embodiment of the invention, the second arm is connected tothe back part of the seat at a joint that includes toothed segments. Thetwo arms are coupled together about a common axis defined by an axialspring element such as torsion bar and/or a spring bar at the head ofthe centre column of the seat support, for the purpose of adjusting thearms with respect to each other. In this embodiment, no lift isnecessary. Rather, adjustment of the seat from the seat to the standposition is carried out by simply moving the second arm (attached to therear part of the seat) upwards, during which the vertical position ofthe rear part of the seat is maintained by the toothed segments of thejoint. At the same time, the front part of the seat can be turned intoan almost vertical position about the hinge between the two parts of theseat.

In a further, fourth embodiment, the torsion or spiral spring connectsto the top of the centre column by a rack and pinion arrangement whichaccommodates shifting of weight relative to the centre column of thework chair.

The third and fourth embodiments comprise mechanisms that include atorsion bar and/or spring bar and a static front (first) arm. The thirdembodiment has a movable rear (second) arm and a centre of gravity thatcan be adjusted in relation to the torsion bar. The adjustment range ofthe lift in the seated position is about 260 mm and the lift range inthe sit/stand position is about 120 mm. In the fourth embodiment, thetorsion bar and/or spiral spring bar is shifted towards the front and upin comparison to the third embodiment, and drives a movable arm thatlifts the back part of the seat into the stand/lean position or height.Another spring element (gas-spring or spiral spring) controlssynchronized movement of the seat back position in connection with thefront torsion bar and/or spiral spring bar and optionally guides thelift mechanism to the stand/lean position. The required adjustment rangeof the lift in the seated position is about 140 mm to about 160 mm. Liftto the stand/sit position is about 200 mm to 220 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more clearly understood, referencewill now be made to the accompanying drawings which illustrate a numberof embodiments of the invention by way of example. FIGS. 1 to 27 areschematic representations.

In the drawings:

FIG. 1 is a side elevational view of a work chair in accordance with afirst embodiment of the invention, shown in the seated position;

FIG. 2 is a side elevational view of the work chair of FIG. 1 in thestanding position;

FIG. 3 is a side elevational view of the work chair of FIG. 1 in therest position;

FIG. 4 is a top plan view of the work chair in the seated position ofFIG. 1;

FIG. 5 is a top plan view of the work chair in the standing position ofFIG. 2;

FIG. 6 is a side elevational view of a work chair in accordance with asecond embodiment of the invention, shown in the seated position;

FIG. 7 is a side elevational view of the work chair according to FIG. 6in the standing position;

FIG. 8 is a side elevational view of the work chair according to FIG. 6in the rest position;

FIG. 9 is a top plan view of the work chair according to FIG. 6 in theseated position;

FIG. 10 is a top plan view of the work chair according to FIG. 7 in thestanding position;

FIGS. 11 to 14 are principal sectional representations of a gas springin various elevated positions of the extended piston of the spring;

FIG. 15 is a side elevational view of a work chair in accordance with athird embodiment of the invention, in the seated position;

FIG. 16 is a side elevational view of the work chair according to FIG.15 in a standing position;

FIG. 17 is a side elevational view of the work chair according to FIG.15 in the rest position;

FIG. 18 is a top plan view of the work chair according to FIG. 15 in theseated position;

FIG. 19 is a top plan view of the work chair according to FIG. 15 in thestanding position;

FIGS. 20 to 22 are representations of rack and pinion arrangements onthe centre column according to the third embodiment of FIGS. 15 to 19;

FIG. 23 is a side elevational view of a work chair in accordance with afourth embodiment of the invention, shown in the seated position;

FIG. 24 is a side elevational view of the work chair according to FIG.23 in the standing position;

FIG. 25 is a side elevational view of the work chair according to FIG.23 in the rest position;

FIG. 26 is a top plan view of the work chair according to FIG. 23 in theseated position;

FIG. 27 is a top plan view of the work chair according to FIG. 23 in thestanding position.

FIG. 28 is a perspective view from above of a chair in accordance withthe fourth embodiment of the invention;

FIG. 29 is an exploded perspective view similar to FIG. 28; and,

FIGS. 30, 31 and 32 are side elevational views showing the chair ofFIGS. 28 and 29 respectively in the normal seating position, sit/standposition and recline/seating position.

DESCRIPTION OF PREFERRED EMBODIMENT

FIGS. 1 to 4 show an adjustable work chair such as an office chair,comprising a centre column 1 which forms part of a “spider” type ofchair base (not shown) having casters for movement across a floor and acushioned, height-adjustable seat made up of a front part 2 and a rearpart 3 that are connected by a hinge 4 that extends transversely of theseat, towards the rear thereof. A back rest 5 extends upwardly from therear part 3 of the seat and can be made separately or in one piece withthe rear part 3. Back rest 5 may be height-adjustable with respect toseat part 3. Part 3 itself is formed with a slight curvature. The frontpart 2 of the seat is generally flat but may be curved at the front.

The centre column 1 includes a gas spring having a telescopicallyextendible piston rod 8 provided at its free end (head 9) with a joint11 which connects to an arm 10 and is provided with a spring elementsuch as a spiral or torsion bar 28 (see FIGS. 20-22), for synchronizingrearward tipping motion. At the same time, the rotational joint 11 isautomatically blocked if lift exceeds 540 mm. Arm 10 as represented inFIGS. 1 to 3 is firmly attached to the underside of the rear seat part 3and attached statically or height-adjustably to the back rest 5. Anotherarm 15 is attached by a rotational joint 16 to the head 12 of thehousing 13 for the gas spring (which forms a lift). The free end of arm15 is coupled to the front seat part 2 near its front end by arotational joint 17. Arm 15 is coupled to the front seat part 2 by wayof a guide mechanism 18. As can be seen from the top views of FIGS. 4and 5, arms 10 and 15 are provided at both sides of the seat (i.e.double arms are used).

FIG. 1 shows the normal seated position of the adjustable work chair inwhich the front and rear parts 2, 3 form an essentially horizontalseating surface. The rear part 3 makes a slightly arched transition intothe back rest 5, which may be adjustable relative to rear seat part 3.

In the embodiment of FIGS. 6 to 10, the front arm 15 is firmly attachedto the fixed head 12 of the column housing 13, in contrast to the firstembodiment of FIGS. 1 to 5. Guide mechanism 18 is longer than in thefirst embodiment.

FIGS. 11 to 14 show the gas spring 7 in the centre column 1. The gasspring 7 is a multi-stage telescopic gas spring, in which a gas spring(piston rod 8) is extendable outwardly from another gas spring (hollowpiston rod 8 ²), which in turn is guided inside a cylinder 13.Technically, up to three gas springs may be coupled together in thisway. Settings 1 and 2 adjust the standard height over an adjustmentrange of 120 mm, according to established requirements. A stand/leanheight of about 800 mm can be achieved with settings 2 and 3.

FIG. 2 shows the piston rod 8 of the gas spring 7 fully extended in thefirst embodiment. This essentially preserves the horizontal position ofthe rear part of the seat 3 at the transition to the back rest 5 bymeans of the arm 10 that is joined to the extendible head 9 of pistonrod 8. However, the seat part 2 has been turned through about 60° fromthe horizontal at the hinge, while arm 15 has rotated to define an acuteangle with piston rod 8. In the stand/lean position, the front part 2 ofthe seat is used for leaning. The legs of the user are slightly angledwhile his or her posterior rests in the trough-like shell at thetransition of the rear seat part 3 to the back rest 5. Therefore, astand/lean/sit position is available to the user to relieve his or herfeet.

In the rest position shown in FIG. 3, arm 10, which fixed firmly to therear seat part 3, has been turned towards the horizontal. The front part2 of the seat tilts through a small angle from the horizontal towardsseat part 3, which is connected with back rest 5, which now slantsrearwardly (synchronized movement). The rotational joint 17 at the freeend of arm 15 has moved closer to the front 6 of the seat part 2, withinguide mechanism 18. In this position, the user of the adjustable workchair can rest.

In the third embodiment of the adjustable chair, represented in FIGS. 15to 18, the centre column 1, the front part 2 of the seat, the rear part3 of the seat, back rest 5 and hinge 4, as well as the front part 6 ofthe seat including the guide mechanism 18 are present in the same manneras in the first and second embodiments according to FIGS. 1 to 10. Thetwo arms 10 and 15, of which arm 15 connects with the guide mechanism 18through a rotational joint 17 also are present. However, there are fourimportant differences from the two earlier embodiments.

The first difference is that arm 10 is not directly attached to the rearpart 3 of the seat but is linked to that part by a joint 20 whichcontains toothed segments so that it can be moved synchronisely. A fixedshaft 22 on the underside of the rear seat part 3 has a toothed segment23 that engages a toothed wheel 24 that is mounted on a fixed shaft 25at the outer end of arm 10. Bearing shells 26 extend around the fixedshaft 22 in such a manner that the toothed segment 23 continuouslyengages the toothed wheel 24. Joint 20 ensures that back rest 5 remainsessentially in a vertical position as it rises from the seated positionof FIG. 15 to the lean/stand position of FIG. 16.

The second difference is that the arm 10 is mounted on a shaft 27 thatis attached to the centre column 1 of the work chair at the height ofhead 12. A spring element, e.g. a torsion bar and/or a spring bar 28(FIGS. 20-22) mounted in shaft 27 makes it possible to adjust the frontseat part 2 from the seated position of FIG. 15 to the stand/leanposition of FIG. 16 by the torque effect of the spring element andpossibly additional torque by a parallelogram motion, and to fold downthe front part 2 of the seat so that between one half and two thirds ofthe area of the seat is folded down while the back part 3 of the seatwith the back rest 5 remains in position. In this case, the entireadjustment range from the upright stand/lean position through theupright seated position to the reclining rest position of FIG. 17 iscontrolled by synchronized movement of the torsion bar and/or spring bar28 in joint 20 within shaft 27.

The third difference is that the front arm 35 is firmly fixed to thehead 12 of centre column 1.

The fourth difference is that a mechanical device is provided forbalancing extreme weight shift, e.g. as in the lean/stand position ofFIG. 16 and the reclining rest position of FIG. 17. This device (30) isshown in three different positions in FIGS. 20 to 22 and is explained inmore detail below.

Shaft 27 carrying the two arms 10, 35 is provided with a torsion barand/or spring bar 28, which is surrounded by a toothed wheel 31 thatengages a horizontal toothed rack 32 fixed on the head 12 of the centrecolumn. Arm 10, which is connected to the rear part 3 of the seatthrough joint 20, acts upon the toothed wheel 31 through shaft 27 insuch manner that the shaft is turned forwardly in the direction of arrow33 in FIG. 21 towards the head 12 of the centre column 1 when raisingarm 10. The load on the work chair in the stand/lean position accordingto FIG. 17 is brought closer to the centre column 1, so that the tiltmoment is considerably reduced. During weight shift backwards into therest position of FIGS. 17 and 22, arm 10 turns clockwise according toarrow 34 and the toothed wheel 31 is turned rearwardly on rack 32, as aresult of which the centre of gravity of the work chair in the restposition of FIG. 17 is located over the centre column 1 of the workchair. Weight balance device 30 permits an extreme frontal lean/standposition and an extreme rearward rest position while ensuring stabilityof the work chair. The entire adjustment range, depending on the size ofthe toothed wheel 27 and the rack 32, typically lies between 2 to 5 cm.The drawings do not show the motion of shaft 27 in device 30 duringhorizontal rolling motion of the toothed wheel 32, or exact alignmentand positioning of the torsion bar 28 in shaft 27.

In a fourth embodiment illustrated in FIGS. 23 to 27, a spring element39 (either a gas spring or a compression spring) is coupled at one endto a fixed arm 35 that extends forwardly from centre column 1 at anangle of about 60°, and includes a piston rod 40 that is coupled to ashaft 25 of joint 20 on the underside on the rear seat part 3. Arm 41connects the shaft 25 of joint 20 with the rotational axis 17 of theguide mechanism 18. By extending the piston rod 40, the front seat part2 is folded almost vertically downwardly as shown in the stand/leanposition of FIG. 24. As in all of the other embodiments, the rear seatpart 3 is lifted together with the back rest 5 by means of arm 41,whereupon the rotational joint 17 of the guide mechanism 18 is movedfrom the rearward position of FIG. 23 to the forward position of FIG.24. The stand/lean position is attained while simultaneously turning thefront seat part 2 into a vertical position.

Instead of the rotational shaft 17, a torsion bar and/or a spring barcan be installed to cause rotational movement into the chair/leanposition. The spring element 39 may then be replaced by a simple guide.

Reference will finally be made to FIGS. 28 to 32 which show a chair inaccordance with the fourth embodiment of the invention (FIGS. 23 to 27)but in which the arm 41 is replaced by a link mechanism that isgenerally indicated at 42. Otherwise, the same reference numerals areused to denote parts that are the same as in FIGS. 23 to 27.

As best seen in FIGS. 30 and 31, arm 35 extends forwardly and upwardlyfrom the top of column 1 generally as in the previous embodiment. A head44 (FIG. 29) extends transversely of the outer end of arm 35 andmechanism 42 is mounted at one end of the head. A second identicalmechanism 42 is mounted at the other end of the head as best seen inFIG. 29. The mechanism includes a pair of links 46 and 48 that extendupwardly from head 44 to the rear seat part 3.

In fact, the two links are coupled to the rear seat part 3 by way of theback 5 of the chair in that upper ends of the respective links 46 and 48are pivoted to one of the upright side members 50 of the back. The rearseat part 3 is attached to a pair of brackets on the side members of theseat, one of which is visible at 52 in FIG. 29. That view also showspivot pins 54 for coupling the links 46, 48 to the side member 50.

Also shown is a transverse bar 56 that extends between the two sidemembers 50 of the back and serves as a mounting point for one end of thegas spring 39 of the chair. Gas spring 39 is shown mounted in a reversedposition as compared with FIGS. 23 to 27 but operates in the samefashion. The spring includes a piston rod 40 that extends downwardly toand is pivotally coupled to the column 1 by pivot pin 58.

Front seat part 2 may be coupled to head 44 by a mechanism similar toguide mechanism 18 referred to previously.

With continued reference to FIG. 29, it will be seen that the two links46 and 48 are pivotally coupled at their ends adjacent column 1 to agear sector element 60 by way of respective pivot pins 62 and 64.Element 60 is in turn mounted on a pivot pin 66 that extendshorizontally outwardly from head 44 parallel to the two pivot pins 62,64 for the links 46, 48. Pin 66 is in fact carried by a disc-shapedelement 68 at the relevant end of head 44 and is capable of a limiteddegree of arcuate movement in a slot 70 in element 68. A similar butdifferently oriented slot 72 is provided in element 68 to receive aninner end portion of the pin 62 for link 46. Pin 62 extends rightthrough gear sector element 60 by way of a further arcuate slot 74 inelement 60. Pin 64 is shorter than pin 62 and does not extend throughelement 60.

Finally, a fixed, toothed sector 76 extends outwardly of disk element 68for engagement with the teeth of gear sector element 60, as best seen inFIGS. 30 to 32. Sector 76 and element 60 are known as “section gears”.

The elements of mechanism 42 that are carried by head 44, and inparticular the arrangement of pivot pins and arcuate slots is designedto cause the sequence of movement of the various components of the chairthat is apparent from a comparison of FIGS. 30 to 31. It will be seenthat link 48 is slotted at 48 a to receive link 46, while permittingindependent relative movement of the links with respect to one another.

As the piston rod 40 of gas spring 39 is extended from the normalseating position of FIG. 30, the links 46, 48 act as a normalparallelogram linkage and the rear seat part 3 and back rest 5 riseparallel to their initial positions. Pivot pins 62 and 66 do not move intheir respective slots 74, 72 and 70. The front seat part 2 folds withrespect to the rear seat part 3. Conversely, if piston rod 40 of gasspring 39 is retracted from the position shown in FIG. 30, the bottomlink 48 is placed in compression and element 60 turns in the clockwisedirection around the fixed teeth 76, causing pivot pins 62 and 66 tomove down in their respective slots 72 and 70 and causing pin 62 to moverearwardly in slot 74, so that the back rest 5 tilts rearwardly to theposition shown in FIG. 32.

It is of course to be understood that the preceding description relatesto particular preferred embodiments of the invention only and that manymodifications are possible within the broad scope of the invention. Someof those modifications have been mentioned and others will be apparentto a person skilled in the art.

I claim:
 1. A chair having a height-adjustable seat comprising a front seat part (2) and a rear seat part (3) connected by a hinge (4) that extends transversely of the seat, the chair further comprising: a lift (14) for raising and lowering the seat, the lift including a fixed part (13) and a movable part (8) that can be extended upwardly with respect to the fixed part (13); a first arm (15) connected between the front part (2) of the seat and the fixed part (13) of the lift, and a second arm (16) connected between the movable part (8) of the lift and the rear part (3) of the seat.
 2. A chair as claimed in claim 1, wherein the first arm (15) is coupled to the fixed part (13) of the lift at a rotational joint (16).
 3. A chair according to claim 1, wherein the fixed part (13) of the lift comprises a centre column (1) supporting the seat, and wherein the first arm (15) is firmly connected to an upper end portion (12) of the centre column (1).
 4. A chair according to any one of claims 1 to 3, wherein the first arm (15) is coupled to the front part (2) of the seat by a guide mechanism (18).
 5. A chair according to any one of claims 1 to 3, wherein the lift comprises a gas spring (7) having an extendable piston (8) including a head (9) which is coupled by a joint to said second arm (10) that extends to the rear part (3) of the seat.
 6. A chair having a height-adjustable seat comprising a front seat part (2) and a rear seat part (3) connected by a hinge (4) that extends transversely of the seat, the chair further comprising: a first arm (15) connected at a joint to the front part (2) of the seat, and a second arm (10) connected to the rear part (3) of the seat at a joint (20) containing toothed segments, the two arms (10, 15) being coupled on a common shaft (27) to a centre support column (1) of the chair and including a spring element (28) permitting adjustment of the arms (10, 15) with respect to each other.
 7. A chair according to claim 6, wherein the common shaft (27) including the spring element (28) is coupled to the centre column (1) by way of a pinion (31) that engages a toothed rack (32) on the top (12) of the centre column (1).
 8. A chair having a height-adjustable seat comprising a front seat part (2) and a rear seat part (3) connected by a hinge (4) that extends transversely of the seat, the chair further comprising a first arm (35) coupled to the front part (2) of the seat at a joint, and a second arm (41) coupled to the rear part (3) of the seat, the first arm (35) being coupled to a centre column (1) of a seat support and being directed forward at an angle of approximately 60°; a spring element (39) being coupled to the first arm (35) intermediate the ends of the arm and having a piston rod (40) coupled to the underside of the rear part (3) of the seat at an axis (25) of a joint coupling; said second arm (41) being coupled to the front part (2) of the seat at a joint (17) on axis (25) by way of a guide mechanism.
 9. A chair having a height-adjustable seat comprising a front seat part (2) and a rear seat part (3) connected by a hinge (4) that extends transversely of the seat, the chair further comprising a first arm means (35) pivotally coupled to the front part (2) of the seat, and a second arm means (35) being coupled to a centre column (1) of a seat support and being directed forwardly towards the front part (2) of the seat; and actuator means coupled between the first arm means (35) and the rear part (2) of the seat for raising and lowering the rear part of the seat between a normal seating position, an elevated sit/stand position, and a reclined position, wherein the second arm means comprises a parallelogram mechanism connected between the rear part of the seat and the first arm means and including a pair of links that cause the rear part of the seat to move between the seated position and the elevated sit/stand position while remaining parallel, the mechanism including section gear means at the ends of the links, adapted to modify motion of the rear part of the seat in moving to said reclined position so that said rear seat part angles downwardly with respect to its orientation in said seated position. 